Conventional snowmobile powertrains incorporate a continuously variable transmission (CVT) having a primary pulley that is operatively coupled to the engine driving shaft and a secondary pulley coupled to a driven shaft. The primary pulley transfers torque to the secondary pulley via a drive belt looped around both pulleys. Typically, the driven shaft is a transverse jackshaft which drives the input member of a chain and sprocket reduction drive. The output of the reduction drive is coupled to one end of an axle on which are located the drive track drive sprocket wheels.
The primary pulley includes centrifugal actuators through which the drive ratio of the primary pulley is varied progressively as a function of the engine speed. The centrifugal actuators are connected to a movable sheave of the primary pulley. The primary pulley also includes a fixed sheave which is axially fixed. The fixed sheave and the movable sheave are rotatable together. The movable sheave is movable axially toward the fixed sheave by the action of the centrifugal actuators and away from the fixed sheave by a biasing spring. The centrifugal actuators generally consist of centrifugal weights in the form of adjusting arms. Each arm is connected to the movable sheave of the primary pulley by a pin, and pivots outwards about its corresponding pin. As they pivot, the arms are in contact with corresponding rollers disposed on a spider fixed relative to the fixed sheave. When the adjusting arms pivot outwards as a result of centrifugal force, the adjusting arms slide against their corresponding roller and the axially movable sheave is pushed towards the fixed sheave.
Axial displacement of the moveable sheave relative to the fixed sheave is provided by the spider, the adjusting arms and the rollers described above. Torque transmission between the fixed and moveable sheaves is provided by separate parts or mechanisms. As a result, axial displacement and torque transmission are provided by functionally separate parts. The use of these separate parts increases the cost and weight of the primary pulley.
Therefore, there is a desire for a pulley for a continuously variable transmission having parts that allow for both axial displacement of the movable sheave and transmission of torque between the movable sheave and the spider, while reducing the cost and weight of the pulley.